A Mixed Blessing

You don't have to dig too deep into this blog to realise I like gulls. There are many reasons, but one is the challenge they sometimes present when it comes to identification. Just lately I have been dead fortunate in having some really interesting gulls pop up in front of me, including four Caspian Gulls, three Yellow-legged Gulls, and one intriguing beast which I haven't written about yet. And then there was this afternoon's contribution...

West Bexington today. It was dull and a bit hazy, with a very fine spray in the air again. This is the scene that greets you as you trudge noisily west on the shingle...

Sea on the left, mere on the right, salty spray-spattered shingle down the middle

I know it looks a bit uninviting in the photo, but honestly it was lovely. The sea was still a bit heavy after yesterday's strongish wind, and every crashing breaker sent a gasp of misty spray up into the breeze. Very atmospheric. I arrived about two-ish, and until I bumped into fellow birder [Sidmouth] Clive Williams near the car park on my departure, not a single soul had been along the beach in well over two hours. Just me, the gulls, and this little chap...

Billy-no-mates Ringed Plover

There was a modest gang of big gulls loafing on the shoreline well along the beach. I know the gulls are pretty skittish here, so made sure I gave them a good grilling from a safe distance. I couldn't see anything of interest, but there were still a few I couldn't see properly, so walked a little closer. Too close. Up they went. Thankfully all were Herring and GBB Gulls.

Next on the agenda was the mere. I approached from the seaward side, just enough so that I could see over the shingle ridge. Hopefully any gulls on the water would see only my scope and my head, and stay put. And that's what happened. First scan through the small flock of 20-30 birds, and one individual jumped out...

L to R: 3rd-winter Herring Gull (foreground), 1stW HG (background), 1st-winter Eye-catcher, 2nd-winter HG, 1st-winter HG, near-ad HG

My first binocular scan of those distant birds made me reach quickly for the scope, and sure enough, that gleaming white head definitely belonged to a 1st-winter bird. Surely a Caspian Gull? Yes, a nicely speckled nape, extending onto the sides of the breast; a pale mantle and scapulars, with not too many bold dark markings. The tertials? Hmm. The greater coverts? Hmmm...

At first glance that bird is so-o-o-o Casp-ish in many ways. But...

Funnily enough, plumage aside, the first off-putting thing for me was the bird's 'look', basically its facial expression, including the bill. To explain what I mean, look at the 1st-winter Herring Gull on the right and imagine it with a white head. I reckon it would be near enough identical. I don't know what it is that gives Caspian Gulls their characteristic 'look' (maybe the position of the eye??) but for me this bird doesn't have it.

A few more pics...

So, what is this bird? First of all, it's not a Herring Gull. I cannot imagine a Herring Gull ever looking as Casp-ish as this. Which leaves two options. It's either a Caspian Gull or a hybrid/backcross thing. To be honest, my views in the field had already persuaded me that it was probably a hybrid, but out of curiosity, and a sense of respect for a smart gull (after all, a bird cannot choose its parents) I put it through the Gibbins et al 'trait-scoring process' as mentioned in this post. There were one or two traits I couldn't accurately gauge from the photos, so erred on the side of caution with them, but mostly it was all doable.

Gibbins et al state that the pure Caspian Gulls in their study scored from 12-25 and the Herring Gulls 29-37. Hybrids scored 22-32, and the authors recommended that no Caspian Gull with a score of 22 or more was safely identifiable as such. Today's bird scored 25. If I'd been able to see a bit more feather detail in the photos it might have dropped a point or two, but I doubt very much it would have scored 21 or less.

Conclusion? I am convinced this is my first Caspian x Herring Gull hybrid. One or both its parents evidently had a healthy dose of Casp genes, but at least one naughty Herring Gull has been dallying where it ought not, somewhere in the family's very recent history. Though of course, that's just my opinion.

All-in-all a fascinating, educational bird. And a perfect example of why I enjoy gulls so much.